Fall, 2013- Chemistry 2311 Homework Problems- Chapter 3 (1) Indicate True (T) or False (F) for each of the following statements: (a) According to Bronsted-Lowry, an acid is a substance that can donate a proton and a base is a substance that can accept a proton. (b) Heterolysis of a carbon-carbon single bond is a bond cleavage process in which one carbon takes both electrons of the original bond leaving the remaining carbon with an empty orbital. (c) According to Lewis, an acid is an electron pair donor and a base is an electron pair acceptor. (d) Ferric chloride is a Lewis acid. (e) Carbocations are Lewis acids. (f) Carbanions are electron deficient electrophilic species. (g) The smaller the value of the pKa, the weaker the acid. (h) The weaker the acid, the stronger the conjugate base. (i) HI is a stronger acid than HCl. (j) Water is a stronger acid than ammonia. (k) Trifluoroacetic acid has a smaller pKa than acetic acid. (l) A hydrogen attached to an sp3 carbon is more acidic than a hydrogen attached to an sp2 carbon. (m) A chloro substituent attached to carbon exhibits an electron donating inductive effect. (n) Exothermic reactions usually have a positive (+) enthalpy of reaction.(o) A negative value of ΔGo is associated with reactions that favor the formation of products when equilibrium is reached. (p) A positive entropy change makes a negative contribution to the change in free energy and is energetically favorable for the formation of products. (q) A protic solvent is one that has a hydrogen atom attached to a strongly electropositive element such as oxygen and nitrogen. (r) Acetate ion is destabilized by the delocalization of the negative charge. (s) The tert-butyl cation is an intermediate in the formation of tert-butyl chloride from the reaction of tert-butyl alcohol with concentrated HCl. (2) Which of the following represents (a) an elimination reaction, (b) a substitution reaction, (c) an addition reaction, and (d) a rearrangement? (a)CCCH3OH3CH HCCCH3OHH3CH (b) ClHNa+ NH2-Liquid NH3 (c) CH2ClCl+K+ CN-CH2CNCl+K+ Cl- (d) CC+Br2CCHBrBrHHH (3) Using curved arrows write equations showing the Lewis acid-base reaction that takes place between the following reaction partners. Indicate the Lewis acid and the Lewis base. (a) Ethanol (C2H5OH) reacts with boron trifluoride (BF3)(b) Dimethyl ether (CH3OCH3) reacts with borane (BH3) (c) tert-Butyl cation [(CH3)3C+] reacts with chloride ion (d) Trimethylamine [(CH3)3N] reacts with trimethylborane [(CH3)3B](4) Acetylene has a pka of 25. Calculate the Ka. The pka of phenol is 9.9. Which is the stronger acid: acetylene or phenol? Calculate the free energies of ionization of acetylene and phenol. (5) Place the following in the order of increasing pKa. (a) Ethane, acetylene (ethyne), and ethylene (ethane)(b) Phenol, ethanol, and acetic acid (c) Fluoroacetic acid, butanoic acid, and acetic acid (6) Complete each of the following reactions. (a)(b) (c) (d) (e) (7) Which of the following compounds is consistent with the accompanying infrared spectrum?(a) (b) (b)
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